// SPDX-License-Identifier: GPL-2.0
// Copyright (c) 2020 Wenbo Zhang
#include <vmlinux.h>
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_core_read.h>
#include <bpf/bpf_tracing.h>
#include "runqlat.h"
#include "bits.bpf.h"
#include "maps.bpf.h"
#include "core_fixes.bpf.h"

#define MAX_ENTRIES 10240
#define TASK_RUNNING 0

const volatile bool filter_cg = false;
const volatile bool targ_per_process = false;
const volatile bool targ_per_thread = false;
const volatile bool targ_per_pidns = false;
const volatile bool targ_ms = false;
const volatile pid_t targ_tgid = 0;

struct {
    __uint(type, BPF_MAP_TYPE_CGROUP_ARRAY);
    __type(key, u32);
    __type(value, u32);
    __uint(max_entries, 1);
} cgroup_map SEC(".maps");

struct {
    __uint(type, BPF_MAP_TYPE_HASH);
    __uint(max_entries, MAX_ENTRIES);
    __type(key, u32);
    __type(value, u64);
} start SEC(".maps");

static struct hist zero;

struct {
    __uint(type, BPF_MAP_TYPE_HASH);
    __uint(max_entries, MAX_ENTRIES);
    __type(key, u32);
    __type(value, struct hist);
} hists SEC(".maps");

static int trace_enqueue(u32 tgid, u32 pid) {
    u64 ts;

    if (!pid)
        return 0;
    if (targ_tgid && targ_tgid != tgid)
        return 0;

    ts = bpf_ktime_get_ns();
    bpf_map_update_elem(&start, &pid, &ts, BPF_ANY);
    return 0;
}

static unsigned int pid_namespace(struct task_struct* task) {
    struct pid* pid;
    unsigned int level;
    struct upid upid;
    unsigned int inum;

    /*  get the pid namespace by following task_active_pid_ns(),
	 *  pid->numbers[pid->level].ns
	 */
    pid = BPF_CORE_READ(task, thread_pid);
    level = BPF_CORE_READ(pid, level);
    bpf_core_read(&upid, sizeof(upid), &pid->numbers[level]);
    inum = BPF_CORE_READ(upid.ns, ns.inum);

    return inum;
}

static int handle_switch(bool preempt,
                         struct task_struct* prev,
                         struct task_struct* next) {
    struct hist* histp;
    u64 *tsp, slot;
    u32 pid, hkey;
    s64 delta;

    if (filter_cg && !bpf_current_task_under_cgroup(&cgroup_map, 0))
        return 0;

    if (get_task_state(prev) == TASK_RUNNING)
        trace_enqueue(BPF_CORE_READ(prev, tgid), BPF_CORE_READ(prev, pid));

    pid = BPF_CORE_READ(next, pid);

    tsp = bpf_map_lookup_elem(&start, &pid);
    if (!tsp)
        return 0;
    delta = bpf_ktime_get_ns() - *tsp;
    if (delta < 0)
        goto cleanup;

    if (targ_per_process)
        hkey = BPF_CORE_READ(next, tgid);
    else if (targ_per_thread)
        hkey = pid;
    else if (targ_per_pidns)
        hkey = pid_namespace(next);
    else
        hkey = -1;
    histp = bpf_map_lookup_or_try_init(&hists, &hkey, &zero);
    if (!histp)
        goto cleanup;
    if (!histp->comm[0])
        bpf_probe_read_kernel_str(&histp->comm, sizeof(histp->comm),
                                  next->comm);
    if (targ_ms)
        delta /= 1000000U;
    else
        delta /= 1000U;
    slot = log2l(delta);
    if (slot >= MAX_SLOTS)
        slot = MAX_SLOTS - 1;
    __sync_fetch_and_add(&histp->slots[slot], 1);

cleanup:
    bpf_map_delete_elem(&start, &pid);
    return 0;
}

SEC("tp_btf/sched_wakeup")
int BPF_PROG(sched_wakeup, struct task_struct* p) {
    if (filter_cg && !bpf_current_task_under_cgroup(&cgroup_map, 0))
        return 0;

    return trace_enqueue(p->tgid, p->pid);
}

SEC("tp_btf/sched_wakeup_new")
int BPF_PROG(sched_wakeup_new, struct task_struct* p) {
    if (filter_cg && !bpf_current_task_under_cgroup(&cgroup_map, 0))
        return 0;

    return trace_enqueue(p->tgid, p->pid);
}

SEC("tp_btf/sched_switch")
int BPF_PROG(sched_switch,
             bool preempt,
             struct task_struct* prev,
             struct task_struct* next) {
    return handle_switch(preempt, prev, next);
}

// SEC("raw_tp/sched_wakeup")
// int BPF_PROG(handle_sched_wakeup, struct task_struct *p)
// {
// 	if (filter_cg && !bpf_current_task_under_cgroup(&cgroup_map, 0))
// 		return 0;

// 	return trace_enqueue(BPF_CORE_READ(p, tgid), BPF_CORE_READ(p, pid));
// }

// SEC("raw_tp/sched_wakeup_new")
// int BPF_PROG(handle_sched_wakeup_new, struct task_struct *p)
// {
// 	if (filter_cg && !bpf_current_task_under_cgroup(&cgroup_map, 0))
// 		return 0;

// 	return trace_enqueue(BPF_CORE_READ(p, tgid), BPF_CORE_READ(p, pid));
// }

// SEC("raw_tp/sched_switch")
// int BPF_PROG(handle_sched_switch, bool preempt, struct task_struct *prev, struct task_struct *next)
// {
// 	return handle_switch(preempt, prev, next);
// }

char LICENSE[] SEC("license") = "GPL";
